Using the place value chart, we can see that the decimal 0.4 is four tenths, so we can write 0.4 as the fraction \(\frac{4}{10}\). Notice however that the fraction is not in lowest terms. We will need to divide the numerator and the denominator by the greatest common factor of 4 and 10 which is 2. Therefore, 0.4 can be written as the fraction \(\frac{2}{5}\), which is in lowest terms.
